security/keys/process_keys.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Manage a process's keyrings
   3  *
   4  * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/init.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/user.h>
  11 #include <linux/keyctl.h>
  12 #include <linux/fs.h>
  13 #include <linux/err.h>
  14 #include <linux/mutex.h>
  15 #include <linux/security.h>
  16 #include <linux/user_namespace.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/init_task.h>
  19 #include <keys/request_key_auth-type.h>
  20 #include "internal.h"
  21
  22 /* Session keyring create vs join semaphore */
  23 static DEFINE_MUTEX(key_session_mutex);
  24
  25 /* The root user's tracking struct */
  26 struct key_user root_key_user = {
  27         .usage          = REFCOUNT_INIT(3),
  28         .cons_lock      = __MUTEX_INITIALIZER(root_key_user.cons_lock),
  29         .lock           = __SPIN_LOCK_UNLOCKED(root_key_user.lock),
  30         .nkeys          = ATOMIC_INIT(2),
  31         .nikeys         = ATOMIC_INIT(2),
  32         .uid            = GLOBAL_ROOT_UID,
  33 };
  34
  35 /*
  36  * Get or create a user register keyring.
  37  */
  38 static struct key *get_user_register(struct user_namespace *user_ns)
  39 {
  40         struct key *reg_keyring = READ_ONCE(user_ns->user_keyring_register);
  41
  42         if (reg_keyring)
  43                 return reg_keyring;
  44
  45         down_write(&user_ns->keyring_sem);
  46
  47         /* Make sure there's a register keyring.  It gets owned by the
  48          * user_namespace's owner.
  49          */
  50         reg_keyring = user_ns->user_keyring_register;
  51         if (!reg_keyring) {
  52                 reg_keyring = keyring_alloc(".user_reg",
  53                                             user_ns->owner, INVALID_GID,
  54                                             &init_cred,
  55                                             KEY_POS_WRITE | KEY_POS_SEARCH |
  56                                             KEY_USR_VIEW | KEY_USR_READ,
  57                                             0,
  58                                             NULL, NULL);
  59                 if (!IS_ERR(reg_keyring))
  60                         smp_store_release(&user_ns->user_keyring_register,
  61                                           reg_keyring);
  62         }
  63
  64         up_write(&user_ns->keyring_sem);
  65
  66         /* We don't return a ref since the keyring is pinned by the user_ns */
  67         return reg_keyring;
  68 }
  69
  70 /*
  71  * Look up the user and user session keyrings for the current process's UID,
  72  * creating them if they don't exist.
  73  */
  74 int look_up_user_keyrings(struct key **_user_keyring,
  75                           struct key **_user_session_keyring)
  76 {
  77         const struct cred *cred = current_cred();
  78         struct user_namespace *user_ns = current_user_ns();
  79         struct key *reg_keyring, *uid_keyring, *session_keyring;
  80         key_perm_t user_keyring_perm;
  81         key_ref_t uid_keyring_r, session_keyring_r;
  82         uid_t uid = from_kuid(user_ns, cred->user->uid);
  83         char buf[20];
  84         int ret;
  85
  86         user_keyring_perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL;
  87
  88         kenter("%u", uid);
  89
  90         reg_keyring = get_user_register(user_ns);
  91         if (IS_ERR(reg_keyring))
  92                 return PTR_ERR(reg_keyring);
  93
  94         down_write(&user_ns->keyring_sem);
  95         ret = 0;
  96
  97         /* Get the user keyring.  Note that there may be one in existence
  98          * already as it may have been pinned by a session, but the user_struct
  99          * pointing to it may have been destroyed by setuid.
 100          */
 101         snprintf(buf, sizeof(buf), "_uid.%u", uid);
 102         uid_keyring_r = keyring_search(make_key_ref(reg_keyring, true),
 103                                        &key_type_keyring, buf, false);
 104         kdebug("_uid %p", uid_keyring_r);
 105         if (uid_keyring_r == ERR_PTR(-EAGAIN)) {
 106                 uid_keyring = keyring_alloc(buf, cred->user->uid, INVALID_GID,
 107                                             cred, user_keyring_perm,
 108                                             KEY_ALLOC_UID_KEYRING |
 109                                             KEY_ALLOC_IN_QUOTA,
 110                                             NULL, reg_keyring);
 111                 if (IS_ERR(uid_keyring)) {
 112                         ret = PTR_ERR(uid_keyring);
 113                         goto error;
 114                 }
 115         } else if (IS_ERR(uid_keyring_r)) {
 116                 ret = PTR_ERR(uid_keyring_r);
 117                 goto error;
 118         } else {
 119                 uid_keyring = key_ref_to_ptr(uid_keyring_r);
 120         }
 121
 122         /* Get a default session keyring (which might also exist already) */
 123         snprintf(buf, sizeof(buf), "_uid_ses.%u", uid);
 124         session_keyring_r = keyring_search(make_key_ref(reg_keyring, true),
 125                                            &key_type_keyring, buf, false);
 126         kdebug("_uid_ses %p", session_keyring_r);
 127         if (session_keyring_r == ERR_PTR(-EAGAIN)) {
 128                 session_keyring = keyring_alloc(buf, cred->user->uid, INVALID_GID,
 129                                                 cred, user_keyring_perm,
 130                                                 KEY_ALLOC_UID_KEYRING |
 131                                                 KEY_ALLOC_IN_QUOTA,
 132                                                 NULL, NULL);
 133                 if (IS_ERR(session_keyring)) {
 134                         ret = PTR_ERR(session_keyring);
 135                         goto error_release;
 136                 }
 137
 138                 /* We install a link from the user session keyring to
 139                  * the user keyring.
 140                  */
 141                 ret = key_link(session_keyring, uid_keyring);
 142                 if (ret < 0)
 143                         goto error_release_session;
 144
 145                 /* And only then link the user-session keyring to the
 146                  * register.
 147                  */
 148                 ret = key_link(reg_keyring, session_keyring);
 149                 if (ret < 0)
 150                         goto error_release_session;
 151         } else if (IS_ERR(session_keyring_r)) {
 152                 ret = PTR_ERR(session_keyring_r);
 153                 goto error_release;
 154         } else {
 155                 session_keyring = key_ref_to_ptr(session_keyring_r);
 156         }
 157
 158         up_write(&user_ns->keyring_sem);
 159
 160         if (_user_session_keyring)
 161                 *_user_session_keyring = session_keyring;
 162         else
 163                 key_put(session_keyring);
 164         if (_user_keyring)
 165                 *_user_keyring = uid_keyring;
 166         else
 167                 key_put(uid_keyring);
 168         kleave(" = 0");
 169         return 0;
 170
 171 error_release_session:
 172         key_put(session_keyring);
 173 error_release:
 174         key_put(uid_keyring);
 175 error:
 176         up_write(&user_ns->keyring_sem);
 177         kleave(" = %d", ret);
 178         return ret;
 179 }
 180
 181 /*
 182  * Get the user session keyring if it exists, but don't create it if it
 183  * doesn't.
 184  */
 185 struct key *get_user_session_keyring_rcu(const struct cred *cred)
 186 {
 187         struct key *reg_keyring = READ_ONCE(cred->user_ns->user_keyring_register);
 188         key_ref_t session_keyring_r;
 189         char buf[20];
 190
 191         struct keyring_search_context ctx = {
 192                 .index_key.type         = &key_type_keyring,
 193                 .index_key.description  = buf,
 194                 .cred                   = cred,
 195                 .match_data.cmp         = key_default_cmp,
 196                 .match_data.raw_data    = buf,
 197                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
 198                 .flags                  = KEYRING_SEARCH_DO_STATE_CHECK,
 199         };
 200
 201         if (!reg_keyring)
 202                 return NULL;
 203
 204         ctx.index_key.desc_len = snprintf(buf, sizeof(buf), "_uid_ses.%u",
 205                                           from_kuid(cred->user_ns,
 206                                                     cred->user->uid));
 207
 208         session_keyring_r = keyring_search_rcu(make_key_ref(reg_keyring, true),
 209                                                &ctx);
 210         if (IS_ERR(session_keyring_r))
 211                 return NULL;
 212         return key_ref_to_ptr(session_keyring_r);
 213 }
 214
 215 /*
 216  * Install a thread keyring to the given credentials struct if it didn't have
 217  * one already.  This is allowed to overrun the quota.
 218  *
 219  * Return: 0 if a thread keyring is now present; -errno on failure.
 220  */
 221 int install_thread_keyring_to_cred(struct cred *new)
 222 {
 223         struct key *keyring;
 224
 225         if (new->thread_keyring)
 226                 return 0;
 227
 228         keyring = keyring_alloc("_tid", new->uid, new->gid, new,
 229                                 KEY_POS_ALL | KEY_USR_VIEW,
 230                                 KEY_ALLOC_QUOTA_OVERRUN,
 231                                 NULL, NULL);
 232         if (IS_ERR(keyring))
 233                 return PTR_ERR(keyring);
 234
 235         new->thread_keyring = keyring;
 236         return 0;
 237 }
 238
 239 /*
 240  * Install a thread keyring to the current task if it didn't have one already.
 241  *
 242  * Return: 0 if a thread keyring is now present; -errno on failure.
 243  */
 244 static int install_thread_keyring(void)
 245 {
 246         struct cred *new;
 247         int ret;
 248
 249         new = prepare_creds();
 250         if (!new)
 251                 return -ENOMEM;
 252
 253         ret = install_thread_keyring_to_cred(new);
 254         if (ret < 0) {
 255                 abort_creds(new);
 256                 return ret;
 257         }
 258
 259         return commit_creds(new);
 260 }
 261
 262 /*
 263  * Install a process keyring to the given credentials struct if it didn't have
 264  * one already.  This is allowed to overrun the quota.
 265  *
 266  * Return: 0 if a process keyring is now present; -errno on failure.
 267  */
 268 int install_process_keyring_to_cred(struct cred *new)
 269 {
 270         struct key *keyring;
 271
 272         if (new->process_keyring)
 273                 return 0;
 274
 275         keyring = keyring_alloc("_pid", new->uid, new->gid, new,
 276                                 KEY_POS_ALL | KEY_USR_VIEW,
 277                                 KEY_ALLOC_QUOTA_OVERRUN,
 278                                 NULL, NULL);
 279         if (IS_ERR(keyring))
 280                 return PTR_ERR(keyring);
 281
 282         new->process_keyring = keyring;
 283         return 0;
 284 }
 285
 286 /*
 287  * Install a process keyring to the current task if it didn't have one already.
 288  *
 289  * Return: 0 if a process keyring is now present; -errno on failure.
 290  */
 291 static int install_process_keyring(void)
 292 {
 293         struct cred *new;
 294         int ret;
 295
 296         new = prepare_creds();
 297         if (!new)
 298                 return -ENOMEM;
 299
 300         ret = install_process_keyring_to_cred(new);
 301         if (ret < 0) {
 302                 abort_creds(new);
 303                 return ret;
 304         }
 305
 306         return commit_creds(new);
 307 }
 308
 309 /*
 310  * Install the given keyring as the session keyring of the given credentials
 311  * struct, replacing the existing one if any.  If the given keyring is NULL,
 312  * then install a new anonymous session keyring.
 313  * @cred can not be in use by any task yet.
 314  *
 315  * Return: 0 on success; -errno on failure.
 316  */
 317 int install_session_keyring_to_cred(struct cred *cred, struct key *keyring)
 318 {
 319         unsigned long flags;
 320         struct key *old;
 321
 322         might_sleep();
 323
 324         /* create an empty session keyring */
 325         if (!keyring) {
 326                 flags = KEY_ALLOC_QUOTA_OVERRUN;
 327                 if (cred->session_keyring)
 328                         flags = KEY_ALLOC_IN_QUOTA;
 329
 330                 keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred,
 331                                         KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
 332                                         flags, NULL, NULL);
 333                 if (IS_ERR(keyring))
 334                         return PTR_ERR(keyring);
 335         } else {
 336                 __key_get(keyring);
 337         }
 338
 339         /* install the keyring */
 340         old = cred->session_keyring;
 341         cred->session_keyring = keyring;
 342
 343         if (old)
 344                 key_put(old);
 345
 346         return 0;
 347 }
 348
 349 /*
 350  * Install the given keyring as the session keyring of the current task,
 351  * replacing the existing one if any.  If the given keyring is NULL, then
 352  * install a new anonymous session keyring.
 353  *
 354  * Return: 0 on success; -errno on failure.
 355  */
 356 static int install_session_keyring(struct key *keyring)
 357 {
 358         struct cred *new;
 359         int ret;
 360
 361         new = prepare_creds();
 362         if (!new)
 363                 return -ENOMEM;
 364
 365         ret = install_session_keyring_to_cred(new, keyring);
 366         if (ret < 0) {
 367                 abort_creds(new);
 368                 return ret;
 369         }
 370
 371         return commit_creds(new);
 372 }
 373
 374 /*
 375  * Handle the fsuid changing.
 376  */
 377 void key_fsuid_changed(struct cred *new_cred)
 378 {
 379         /* update the ownership of the thread keyring */
 380         if (new_cred->thread_keyring) {
 381                 down_write(&new_cred->thread_keyring->sem);
 382                 new_cred->thread_keyring->uid = new_cred->fsuid;
 383                 up_write(&new_cred->thread_keyring->sem);
 384         }
 385 }
 386
 387 /*
 388  * Handle the fsgid changing.
 389  */
 390 void key_fsgid_changed(struct cred *new_cred)
 391 {
 392         /* update the ownership of the thread keyring */
 393         if (new_cred->thread_keyring) {
 394                 down_write(&new_cred->thread_keyring->sem);
 395                 new_cred->thread_keyring->gid = new_cred->fsgid;
 396                 up_write(&new_cred->thread_keyring->sem);
 397         }
 398 }
 399
 400 /*
 401  * Search the process keyrings attached to the supplied cred for the first
 402  * matching key under RCU conditions (the caller must be holding the RCU read
 403  * lock).
 404  *
 405  * The search criteria are the type and the match function.  The description is
 406  * given to the match function as a parameter, but doesn't otherwise influence
 407  * the search.  Typically the match function will compare the description
 408  * parameter to the key's description.
 409  *
 410  * This can only search keyrings that grant Search permission to the supplied
 411  * credentials.  Keyrings linked to searched keyrings will also be searched if
 412  * they grant Search permission too.  Keys can only be found if they grant
 413  * Search permission to the credentials.
 414  *
 415  * Returns a pointer to the key with the key usage count incremented if
 416  * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only
 417  * matched negative keys.
 418  *
 419  * In the case of a successful return, the possession attribute is set on the
 420  * returned key reference.
 421  */
 422 key_ref_t search_cred_keyrings_rcu(struct keyring_search_context *ctx)
 423 {
 424         struct key *user_session;
 425         key_ref_t key_ref, ret, err;
 426         const struct cred *cred = ctx->cred;
 427
 428         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
 429          * searchable, but we failed to find a key or we found a negative key;
 430          * otherwise we want to return a sample error (probably -EACCES) if
 431          * none of the keyrings were searchable
 432          *
 433          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
 434          */
 435         key_ref = NULL;
 436         ret = NULL;
 437         err = ERR_PTR(-EAGAIN);
 438
 439         /* search the thread keyring first */
 440         if (cred->thread_keyring) {
 441                 key_ref = keyring_search_rcu(
 442                         make_key_ref(cred->thread_keyring, 1), ctx);
 443                 if (!IS_ERR(key_ref))
 444                         goto found;
 445
 446                 switch (PTR_ERR(key_ref)) {
 447                 case -EAGAIN: /* no key */
 448                 case -ENOKEY: /* negative key */
 449                         ret = key_ref;
 450                         break;
 451                 default:
 452                         err = key_ref;
 453                         break;
 454                 }
 455         }
 456
 457         /* search the process keyring second */
 458         if (cred->process_keyring) {
 459                 key_ref = keyring_search_rcu(
 460                         make_key_ref(cred->process_keyring, 1), ctx);
 461                 if (!IS_ERR(key_ref))
 462                         goto found;
 463
 464                 switch (PTR_ERR(key_ref)) {
 465                 case -EAGAIN: /* no key */
 466                         if (ret)
 467                                 break;
 468                         /* fall through */
 469                 case -ENOKEY: /* negative key */
 470                         ret = key_ref;
 471                         break;
 472                 default:
 473                         err = key_ref;
 474                         break;
 475                 }
 476         }
 477
 478         /* search the session keyring */
 479         if (cred->session_keyring) {
 480                 key_ref = keyring_search_rcu(
 481                         make_key_ref(cred->session_keyring, 1), ctx);
 482
 483                 if (!IS_ERR(key_ref))
 484                         goto found;
 485
 486                 switch (PTR_ERR(key_ref)) {
 487                 case -EAGAIN: /* no key */
 488                         if (ret)
 489                                 break;
 490                         /* fall through */
 491                 case -ENOKEY: /* negative key */
 492                         ret = key_ref;
 493                         break;
 494                 default:
 495                         err = key_ref;
 496                         break;
 497                 }
 498         }
 499         /* or search the user-session keyring */
 500         else if ((user_session = get_user_session_keyring_rcu(cred))) {
 501                 key_ref = keyring_search_rcu(make_key_ref(user_session, 1),
 502                                              ctx);
 503                 key_put(user_session);
 504
 505                 if (!IS_ERR(key_ref))
 506                         goto found;
 507
 508                 switch (PTR_ERR(key_ref)) {
 509                 case -EAGAIN: /* no key */
 510                         if (ret)
 511                                 break;
 512                         /* fall through */
 513                 case -ENOKEY: /* negative key */
 514                         ret = key_ref;
 515                         break;
 516                 default:
 517                         err = key_ref;
 518                         break;
 519                 }
 520         }
 521
 522         /* no key - decide on the error we're going to go for */
 523         key_ref = ret ? ret : err;
 524
 525 found:
 526         return key_ref;
 527 }
 528
 529 /*
 530  * Search the process keyrings attached to the supplied cred for the first
 531  * matching key in the manner of search_my_process_keyrings(), but also search
 532  * the keys attached to the assumed authorisation key using its credentials if
 533  * one is available.
 534  *
 535  * The caller must be holding the RCU read lock.
 536  *
 537  * Return same as search_cred_keyrings_rcu().
 538  */
 539 key_ref_t search_process_keyrings_rcu(struct keyring_search_context *ctx)
 540 {
 541         struct request_key_auth *rka;
 542         key_ref_t key_ref, ret = ERR_PTR(-EACCES), err;
 543
 544         key_ref = search_cred_keyrings_rcu(ctx);
 545         if (!IS_ERR(key_ref))
 546                 goto found;
 547         err = key_ref;
 548
 549         /* if this process has an instantiation authorisation key, then we also
 550          * search the keyrings of the process mentioned there
 551          * - we don't permit access to request_key auth keys via this method
 552          */
 553         if (ctx->cred->request_key_auth &&
 554             ctx->cred == current_cred() &&
 555             ctx->index_key.type != &key_type_request_key_auth
 556             ) {
 557                 const struct cred *cred = ctx->cred;
 558
 559                 if (key_validate(cred->request_key_auth) == 0) {
 560                         rka = ctx->cred->request_key_auth->payload.data[0];
 561
 562                         //// was search_process_keyrings() [ie. recursive]
 563                         ctx->cred = rka->cred;
 564                         key_ref = search_cred_keyrings_rcu(ctx);
 565                         ctx->cred = cred;
 566
 567                         if (!IS_ERR(key_ref))
 568                                 goto found;
 569                         ret = key_ref;
 570                 }
 571         }
 572
 573         /* no key - decide on the error we're going to go for */
 574         if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY))
 575                 key_ref = ERR_PTR(-ENOKEY);
 576         else if (err == ERR_PTR(-EACCES))
 577                 key_ref = ret;
 578         else
 579                 key_ref = err;
 580
 581 found:
 582         return key_ref;
 583 }
 584 /*
 585  * See if the key we're looking at is the target key.
 586  */
 587 bool lookup_user_key_possessed(const struct key *key,
 588                                const struct key_match_data *match_data)
 589 {
 590         return key == match_data->raw_data;
 591 }
 592
 593 /*
 594  * Look up a key ID given us by userspace with a given permissions mask to get
 595  * the key it refers to.
 596  *
 597  * Flags can be passed to request that special keyrings be created if referred
 598  * to directly, to permit partially constructed keys to be found and to skip
 599  * validity and permission checks on the found key.
 600  *
 601  * Returns a pointer to the key with an incremented usage count if successful;
 602  * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond
 603  * to a key or the best found key was a negative key; -EKEYREVOKED or
 604  * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the
 605  * found key doesn't grant the requested permit or the LSM denied access to it;
 606  * or -ENOMEM if a special keyring couldn't be created.
 607  *
 608  * In the case of a successful return, the possession attribute is set on the
 609  * returned key reference.
 610  */
 611 key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags,
 612                           key_perm_t perm)
 613 {
 614         struct keyring_search_context ctx = {
 615                 .match_data.cmp         = lookup_user_key_possessed,
 616                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
 617                 .flags                  = (KEYRING_SEARCH_NO_STATE_CHECK |
 618                                            KEYRING_SEARCH_RECURSE),
 619         };
 620         struct request_key_auth *rka;
 621         struct key *key, *user_session;
 622         key_ref_t key_ref, skey_ref;
 623         int ret;
 624
 625 try_again:
 626         ctx.cred = get_current_cred();
 627         key_ref = ERR_PTR(-ENOKEY);
 628
 629         switch (id) {
 630         case KEY_SPEC_THREAD_KEYRING:
 631                 if (!ctx.cred->thread_keyring) {
 632                         if (!(lflags & KEY_LOOKUP_CREATE))
 633                                 goto error;
 634
 635                         ret = install_thread_keyring();
 636                         if (ret < 0) {
 637                                 key_ref = ERR_PTR(ret);
 638                                 goto error;
 639                         }
 640                         goto reget_creds;
 641                 }
 642
 643                 key = ctx.cred->thread_keyring;
 644                 __key_get(key);
 645                 key_ref = make_key_ref(key, 1);
 646                 break;
 647
 648         case KEY_SPEC_PROCESS_KEYRING:
 649                 if (!ctx.cred->process_keyring) {
 650                         if (!(lflags & KEY_LOOKUP_CREATE))
 651                                 goto error;
 652
 653                         ret = install_process_keyring();
 654                         if (ret < 0) {
 655                                 key_ref = ERR_PTR(ret);
 656                                 goto error;
 657                         }
 658                         goto reget_creds;
 659                 }
 660
 661                 key = ctx.cred->process_keyring;
 662                 __key_get(key);
 663                 key_ref = make_key_ref(key, 1);
 664                 break;
 665
 666         case KEY_SPEC_SESSION_KEYRING:
 667                 if (!ctx.cred->session_keyring) {
 668                         /* always install a session keyring upon access if one
 669                          * doesn't exist yet */
 670                         ret = look_up_user_keyrings(NULL, &user_session);
 671                         if (ret < 0)
 672                                 goto error;
 673                         if (lflags & KEY_LOOKUP_CREATE)
 674                                 ret = join_session_keyring(NULL);
 675                         else
 676                                 ret = install_session_keyring(user_session);
 677
 678                         key_put(user_session);
 679                         if (ret < 0)
 680                                 goto error;
 681                         goto reget_creds;
 682                 } else if (test_bit(KEY_FLAG_UID_KEYRING,
 683                                     &ctx.cred->session_keyring->flags) &&
 684                            lflags & KEY_LOOKUP_CREATE) {
 685                         ret = join_session_keyring(NULL);
 686                         if (ret < 0)
 687                                 goto error;
 688                         goto reget_creds;
 689                 }
 690
 691                 key = ctx.cred->session_keyring;
 692                 __key_get(key);
 693                 key_ref = make_key_ref(key, 1);
 694                 break;
 695
 696         case KEY_SPEC_USER_KEYRING:
 697                 ret = look_up_user_keyrings(&key, NULL);
 698                 if (ret < 0)
 699                         goto error;
 700                 key_ref = make_key_ref(key, 1);
 701                 break;
 702
 703         case KEY_SPEC_USER_SESSION_KEYRING:
 704                 ret = look_up_user_keyrings(NULL, &key);
 705                 if (ret < 0)
 706                         goto error;
 707                 key_ref = make_key_ref(key, 1);
 708                 break;
 709
 710         case KEY_SPEC_GROUP_KEYRING:
 711                 /* group keyrings are not yet supported */
 712                 key_ref = ERR_PTR(-EINVAL);
 713                 goto error;
 714
 715         case KEY_SPEC_REQKEY_AUTH_KEY:
 716                 key = ctx.cred->request_key_auth;
 717                 if (!key)
 718                         goto error;
 719
 720                 __key_get(key);
 721                 key_ref = make_key_ref(key, 1);
 722                 break;
 723
 724         case KEY_SPEC_REQUESTOR_KEYRING:
 725                 if (!ctx.cred->request_key_auth)
 726                         goto error;
 727
 728                 down_read(&ctx.cred->request_key_auth->sem);
 729                 if (test_bit(KEY_FLAG_REVOKED,
 730                              &ctx.cred->request_key_auth->flags)) {
 731                         key_ref = ERR_PTR(-EKEYREVOKED);
 732                         key = NULL;
 733                 } else {
 734                         rka = ctx.cred->request_key_auth->payload.data[0];
 735                         key = rka->dest_keyring;
 736                         __key_get(key);
 737                 }
 738                 up_read(&ctx.cred->request_key_auth->sem);
 739                 if (!key)
 740                         goto error;
 741                 key_ref = make_key_ref(key, 1);
 742                 break;
 743
 744         default:
 745                 key_ref = ERR_PTR(-EINVAL);
 746                 if (id < 1)
 747                         goto error;
 748
 749                 key = key_lookup(id);
 750                 if (IS_ERR(key)) {
 751                         key_ref = ERR_CAST(key);
 752                         goto error;
 753                 }
 754
 755                 key_ref = make_key_ref(key, 0);
 756
 757                 /* check to see if we possess the key */
 758                 ctx.index_key                   = key->index_key;
 759                 ctx.match_data.raw_data         = key;
 760                 kdebug("check possessed");
 761                 rcu_read_lock();
 762                 skey_ref = search_process_keyrings_rcu(&ctx);
 763                 rcu_read_unlock();
 764                 kdebug("possessed=%p", skey_ref);
 765
 766                 if (!IS_ERR(skey_ref)) {
 767                         key_put(key);
 768                         key_ref = skey_ref;
 769                 }
 770
 771                 break;
 772         }
 773
 774         /* unlink does not use the nominated key in any way, so can skip all
 775          * the permission checks as it is only concerned with the keyring */
 776         if (lflags & KEY_LOOKUP_FOR_UNLINK) {
 777                 ret = 0;
 778                 goto error;
 779         }
 780
 781         if (!(lflags & KEY_LOOKUP_PARTIAL)) {
 782                 ret = wait_for_key_construction(key, true);
 783                 switch (ret) {
 784                 case -ERESTARTSYS:
 785                         goto invalid_key;
 786                 default:
 787                         if (perm)
 788                                 goto invalid_key;
 789                 case 0:
 790                         break;
 791                 }
 792         } else if (perm) {
 793                 ret = key_validate(key);
 794                 if (ret < 0)
 795                         goto invalid_key;
 796         }
 797
 798         ret = -EIO;
 799         if (!(lflags & KEY_LOOKUP_PARTIAL) &&
 800             key_read_state(key) == KEY_IS_UNINSTANTIATED)
 801                 goto invalid_key;
 802
 803         /* check the permissions */
 804         ret = key_task_permission(key_ref, ctx.cred, perm);
 805         if (ret < 0)
 806                 goto invalid_key;
 807
 808         key->last_used_at = ktime_get_real_seconds();
 809
 810 error:
 811         put_cred(ctx.cred);
 812         return key_ref;
 813
 814 invalid_key:
 815         key_ref_put(key_ref);
 816         key_ref = ERR_PTR(ret);
 817         goto error;
 818
 819         /* if we attempted to install a keyring, then it may have caused new
 820          * creds to be installed */
 821 reget_creds:
 822         put_cred(ctx.cred);
 823         goto try_again;
 824 }
 825 EXPORT_SYMBOL(lookup_user_key);
 826
 827 /*
 828  * Join the named keyring as the session keyring if possible else attempt to
 829  * create a new one of that name and join that.
 830  *
 831  * If the name is NULL, an empty anonymous keyring will be installed as the
 832  * session keyring.
 833  *
 834  * Named session keyrings are joined with a semaphore held to prevent the
 835  * keyrings from going away whilst the attempt is made to going them and also
 836  * to prevent a race in creating compatible session keyrings.
 837  */
 838 long join_session_keyring(const char *name)
 839 {
 840         const struct cred *old;
 841         struct cred *new;
 842         struct key *keyring;
 843         long ret, serial;
 844
 845         new = prepare_creds();
 846         if (!new)
 847                 return -ENOMEM;
 848         old = current_cred();
 849
 850         /* if no name is provided, install an anonymous keyring */
 851         if (!name) {
 852                 ret = install_session_keyring_to_cred(new, NULL);
 853                 if (ret < 0)
 854                         goto error;
 855
 856                 serial = new->session_keyring->serial;
 857                 ret = commit_creds(new);
 858                 if (ret == 0)
 859                         ret = serial;
 860                 goto okay;
 861         }
 862
 863         /* allow the user to join or create a named keyring */
 864         mutex_lock(&key_session_mutex);
 865
 866         /* look for an existing keyring of this name */
 867         keyring = find_keyring_by_name(name, false);
 868         if (PTR_ERR(keyring) == -ENOKEY) {
 869                 /* not found - try and create a new one */
 870                 keyring = keyring_alloc(
 871                         name, old->uid, old->gid, old,
 872                         KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ | KEY_USR_LINK,
 873                         KEY_ALLOC_IN_QUOTA, NULL, NULL);
 874                 if (IS_ERR(keyring)) {
 875                         ret = PTR_ERR(keyring);
 876                         goto error2;
 877                 }
 878         } else if (IS_ERR(keyring)) {
 879                 ret = PTR_ERR(keyring);
 880                 goto error2;
 881         } else if (keyring == new->session_keyring) {
 882                 ret = 0;
 883                 goto error3;
 884         }
 885
 886         /* we've got a keyring - now to install it */
 887         ret = install_session_keyring_to_cred(new, keyring);
 888         if (ret < 0)
 889                 goto error3;
 890
 891         commit_creds(new);
 892         mutex_unlock(&key_session_mutex);
 893
 894         ret = keyring->serial;
 895         key_put(keyring);
 896 okay:
 897         return ret;
 898
 899 error3:
 900         key_put(keyring);
 901 error2:
 902         mutex_unlock(&key_session_mutex);
 903 error:
 904         abort_creds(new);
 905         return ret;
 906 }
 907
 908 /*
 909  * Replace a process's session keyring on behalf of one of its children when
 910  * the target  process is about to resume userspace execution.
 911  */
 912 void key_change_session_keyring(struct callback_head *twork)
 913 {
 914         const struct cred *old = current_cred();
 915         struct cred *new = container_of(twork, struct cred, rcu);
 916
 917         if (unlikely(current->flags & PF_EXITING)) {
 918                 put_cred(new);
 919                 return;
 920         }
 921
 922         new->  uid      = old->  uid;
 923         new-> euid      = old-> euid;
 924         new-> suid      = old-> suid;
 925         new->fsuid      = old->fsuid;
 926         new->  gid      = old->  gid;
 927         new-> egid      = old-> egid;
 928         new-> sgid      = old-> sgid;
 929         new->fsgid      = old->fsgid;
 930         new->user       = get_uid(old->user);
 931         new->user_ns    = get_user_ns(old->user_ns);
 932         new->group_info = get_group_info(old->group_info);
 933
 934         new->securebits = old->securebits;
 935         new->cap_inheritable    = old->cap_inheritable;
 936         new->cap_permitted      = old->cap_permitted;
 937         new->cap_effective      = old->cap_effective;
 938         new->cap_ambient        = old->cap_ambient;
 939         new->cap_bset           = old->cap_bset;
 940
 941         new->jit_keyring        = old->jit_keyring;
 942         new->thread_keyring     = key_get(old->thread_keyring);
 943         new->process_keyring    = key_get(old->process_keyring);
 944
 945         security_transfer_creds(new, old);
 946
 947         commit_creds(new);
 948 }
 949
 950 /*
 951  * Make sure that root's user and user-session keyrings exist.
 952  */
 953 static int __init init_root_keyring(void)
 954 {
 955         return look_up_user_keyrings(NULL, NULL);
 956 }
 957
 958 late_initcall(init_root_keyring);